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运用相场方法研究双晶体NiTi形状记忆合金分别在无应力和有应力作用下时效过程中Ni4Ti3相的沉淀行为,模拟研究两种不同初始过饱和度(Ni含量分别为51.5%和52.5%,摩尔分数)的NiTi基体并考虑外加应力的影响。模拟结果表明,在无应力作用的体系中,当体系Ni原子初始浓度相对较低(51.5%Ni)时,Ni4Ti3相以非均匀的方式析出,其中晶界上存在大量的Ni4Ti3变体,晶界内大部分区域无变体;当体系Ni原子初始浓度较高(52.5%Ni)时,Ni4Ti3在整个双晶体系中均匀析出。在所研究的两种初始浓度下,一定大小的外加应力将直接导致Ni4Ti3变体在整个模拟体系中均匀析出,而两晶粒中变体的类型分布有所不同。
The phase behavior method was used to study the precipitation behavior of Ni4Ti3 phase in the dual-crystal NiTi shape memory alloy under stress-free and stress-aging conditions respectively. The effects of two different initial supersaturations (Ni contents of 51.5% and 52.5%, respectively Fraction) NiTi matrix and consider the effect of applied stress. The simulation results show that Ni4Ti3 phase precipitates in a non-uniform manner when the initial concentration of Ni atoms is relatively low (51.5% Ni) in the unstressed system. There are a large number of Ni4Ti3 variants in the grain boundaries, Ni4Ti3 is uniformly precipitated in the whole twin system when the initial concentration of Ni atom in the system is high (52.5% Ni). At the two initial concentrations studied, a certain amount of applied stress will directly result in the uniform precipitation of the Ni4Ti3 variant throughout the simulated system, with variations in the type distribution of the two grains.